Polygonal spring coupling

ABSTRACT

A polygonal coupling couples torque source to a torque consumer such that input and output portions of the coupling may elastically rotate relative to one another during torque transfer to accommodate rotational speed variations in delivery of torque from the torque source. In an embodiment the torque source is an internal combustion engine with an integrated switchable coupling between the engine crankshaft and a torque transfer segment supporting a motor-generator. The polygonal coupling includes axially-overlapping polygonal-shaped male and female portions which cooperate to pass torque between the output of the integrated switchable coupling and an input of the torque transfer segment. At least one of the male and female portions includes recesses which form flexible arms adjacent to the lobes of the polygonal shape that allow the portions to rotate relative to one another over small angular displacements, and thereby improve damping of crankshaft rotational vibrations.

This application is a continuation-in-part application claiming priorityto U.S. application Ser. No. 16/008,679, filed Jun. 14, 2018.

The present invention relates to couplings across which torque istransferred, in particular to a coupling for use in a variety ofindustrial applications, such as in a hybrid electric generating andstorage system associated with an internal combustion engine.

BACKGROUND OF THE INVENTION

Hybrid electric vehicles having an internal combustion engine combinedwith a motor-generator and an electrical energy storage system have beenthe focus of considerable attention in the automotive field,particularly in the field of passenger vehicles. Development of hybridelectric vehicle systems has only recently begun to attract significantinterest in commercial and off-road vehicles, e.g., trucks and busses inVehicle Classes 2-8, in earth-moving equipment and railroadapplications, and in stationary internal combustion engine-poweredinstallations.

U.S. patent application Ser. No. 15/378,139, assigned to the presentApplicant and incorporated by reference in full herein, discloses anovel approach to providing the benefits of hybrid electric technologiesin which a hybrid electric vehicle system is located at a front end ofan engine, with a motor-generator being arranged in a manner thatrequires little or no extension of the length of the front of thevehicle. This system is referred to as a front end motor-generator or“FEMG” system.

As used in this description, the “front end” of the engine is the endopposite the end from which engine-generated torque output istransferred to the primary torque consumers, such as a vehicle'stransmission and drive axles or a stationary engine installation's load,such as a pump drive. Typically, the rear end of an engine is where theengine's flywheel is located, and the front end is where components suchas engine-driven accessories are located (e.g., air conditioning andcompressed air compressors, engine cooling fans, coolant pumps, powersteering pumps).

In this front end motor-generator system, the motor-generator is locatedin the front region of the engine, laterally offset to the side of therotation axis of the engine crankshaft, and is supported on a torquetransfer segment (also referred to as a “drive unit”) between themotor-generator and the region immediately in front of the front end ofthe engine's crankshaft. The torque transfer segment may take the formof a narrow-depth parallel shaft gearbox arranged with its inputrotation axis co-axial with the engine crankshaft.

An important feature of the front end generator system is that themotor-generator exchanges torque with the engine crankshaft via thetorque transfer segment and a switchable coupling (i.e., disengageable)between the torque transfer segment and the front end of the crankshaft.The switchable coupling includes an engine-side portion coupled directlyto the engine crankshaft, a drive portion engageable with theengine-side portion to transfer torque therebetween, and an engagementdevice, preferably an axially-actuated clutch between the drive portionand the engine-side portion. The engine-side portion of the couplingincludes a crankshaft vibration damper (hereafter, a “damper”), unlike aconventional crankshaft damper that traditionally has been a separateelement fixed to the crankshaft as a dedicated crankshaft vibrationsuppression device. This arrangement enables transfer of torque betweenthe accessory drive, the motor-generator and the engine in a flexiblemanner, for example, having the accessory drive being driven bydifferent torque sources (e.g., the engine and/or the motor-generator),having the engine being the source of torque to drive themotor-generator as an electric generator, and/or having themotor-generator coupled to the engine and operated as a motor to act asa supplemental vehicle propulsion torque source.

Particularly preferably, the switchable coupling is an integratedclutch-pulley-damper unit having the clutch between the engine sidedamper portion and the drive portion. The drive side portion includes adrive flange configured to be coupled to the engine-end of the torquetransfer segment, the drive flange also including one or more drivepulley sections on its outer circumference. This preferred configurationalso has all three of the pulley, clutch and damper arrangedconcentrically, with at least two of these elements partiallyoverlapping one another along their rotation axis. This arrangementresults in a disengageable coupling with a greatly minimized axial depthto facilitate FEMG mounting in the space-constrained environment infront of an engine. The axial depth of the coupling may be furtherminimized by reducing the axial depth of the clutch, pulley and damperto a point at which the drive pulley extends concentrically around allor at least substantially all of the clutch and the engine-side damperportion of the coupling.

Alternatively, one or more of the three clutch, pulley and damperportions may be arranged co-axially with, but not axially overlappingthe other portions as needed to suit the particular front endarrangements of engines from different engine suppliers. For example, inan engine application in which a belt drive is not aligned with thedamper (i.e., the damper does not have belt-driving grooves about itsouter circumference, such as in some Cummins® engine arrangements), thebelt-driving surface of the pulley portion of the coupling need notaxially overlap the damper. In other applications having belt drivesurfaces on the outer circumference of the damper and a further beltdrive surface on a pulley mounted in front of the damper, such as insome Detroit Diesel® engines, the coupling that would be used in placeof the original damper and pulley may be arranged with both belt drivesurfaces on a pulley that extends axially over the damper (i.e., thedamper axially overlaps substantially all of both the damper and theclutch), or with a belt drive surface on the outer circumference of thedamper, for example, to drive engine accessories that are neverdisconnected from the crankshaft, such as an engine coolant pump, whileanother other belt drive surface is located on the pulley member thatextends axially over the clutch.

Previously, crankshaft dampers were typically designed with an outerportion, typically a concentric ring, resiliently connected to an innerhub of the damper directly mounted on the front end of the crankshaft.Such dampers were designed such that the inertia of the outer portionwould permit the outer portion to concentrically oscillate about theinner hub at a frequency that effectively matched and offset crankshaftrotation vibrations (i.e., small angular irregularities in thecrankshaft's rotation caused by “micro” accelerations and decelerationsof the crankshaft associated with individual force pulses applied to thecrankshaft, e.g., individual cylinder combustion events, individualcylinder compression stroke resistance, etc.). Left unaddressed, thesecrankshaft rotational speed oscillations can cause significant damage tothe engine's internal components.

The addition of a switchable coupling, such as the clutch-pulley-damperunit disclosed in application Ser. No. 15/378,139, to the front end of acrankshaft has the potential to alter the torsional stiffness seen bythe crankshaft when the switchable coupling is closed and the torquetransfer segment is thereby coupled to the crankshaft. When so coupled,the torque transfer segment gear train and the attached motor-generatormay present the crankshaft with increased inertia which can impact thenatural frequency of the mass elastic system. The result can be lesseffective damping of the crankshaft vibrations than desired.

The present invention provides a switchable coupling which addressesthis problem by including a resilient portion in theclutch-pulley-damper unit that effectively isolates much of theadditional inertia of the torque transfer segment and motor-generatorfrom the engine crankshaft.

Preferably, at the point at which the drive input to the torque transfersegment is coupled to the output of the switchable coupling (in theclutch-pulley-damper unit and gearbox in application Ser. No.15/378,139, via a male-female spline connection), a polygonal-shapedcoupling is provided, with at least one of the male and female polygonalportions having area in which additional flexibility is incorporated.For example, on the male side of a triangular polygonal coupling, neareach of the three corners a slot (or other geometry) may be providedthat allows each corner to slightly flex when loaded by angularvibration pulses from the crankshaft. Such an arrangement would allowthe male portion of the torque transfer segment-to-switchable couplingarrangement to rotate slightly relative to the female portion inresponse to the crankshaft vibrations. The present invention is notlimited to a slot configuration, but may use any aperture geometry theprovides the desired amount of resilient response to crankshaftacceleration/deceleration pulses.

With the present invention's the use of a polygonal drive arrangementwith vibration-absorbing features, the crankshaft is effectivelyisolated from the inertia of the torque transfer segment andmotor-generator by the vibration-absorbing features. Theclutch-pulley-damper unit therefore may be designed in a manner thatkeeps its vibration response range seen by the crankshaft in the rangeof the crankshaft vibrations, yet ensure the crankshaft is still able totransmit its full drive torque to the torque transfer segment and themotor-generator.

The shape of the polygonal coupling is not limited to a triangularpolygon, but instead may have any number of sides, as long as thepolygon is modified to induce the desired coupling flexibility as in thetriangular example. Moreover, the present invention is not limited toany particular shape (e.g., oval, dog-bone), as long as thevibration-absorbing portions of the shape permit the coupling to absorbcircumferential vibrations while still maintaining the ability totransfer torque output from the crankshaft to the torque transfersegment, as would a splined coupling.

An additional factor to consider in the design of the present inventionis the ratio of torsional strength to torsional stiffness of thecoupling. The torsional stiffness of the coupling is reduced withdecreasing stiffness of the portions of the coupling at the corners ofthe polygon, which allows the corners to slightly flex in response toangular vibration pulses, for example by including transverse breaks inportions of the coupling that are radially adjacent tocircumferentially-oriented recesses at each apex, thereby formingseparate circumferentially-oriented “arms” that can independently flex.Similarly, the ratio of torsional flexibility to torsional strength maybe increased by omitting such breaks, resulting in a solid “bridge”section between a recess and the axial face of the coupling part. Theresult is a stiffer, but to an even greater degree stronger, arrangementthat increases the ratio of torsional strength to torsional stiffness.The torsional strength/weight ratio may also be altered by altering therelative sizes of the circumferentially-aligned recesses relative to thethickness of the radially adjacent portions.

Regardless of the specific approach taken, it is desirable to have theratio of torsional strength to torsional stiffness to be optimized forthe application, particularly where the resonant frequency is to be keptas low as possible.

A further aspect of the present invention is the opportunity to provideincreased vibration damping in the coupling, by including a dampingmedium in the recesses. A small amount of damping is provided inherentlyby the coupling material's elasticity (i.e., a small amount of energydissipation in the form of heat generated by friction between componentsand hysteresis of the material as it is compressed and tensioned inresponse to vibrations). This damping may be significantly increased bythe additional of a damping medium in the coupling recesses,particularly in embodiments in which the arms are separated and thuscapable of greater relative movement. Suitable damping materials includean elastomer, wax, a sponge-like material and/or another materialcapable of dissipating kinetic energy generated by relative movements inresponse to angular vibrations.

The polygonal coupling of the present invention is not limited to use infront end motor-generator systems, or to applications in which aninternal combustion engine is present. The potential applications of theinventive polygonal coupling include any application in which torque istransferred over a rotating coupling, such as between driven and adriving shafts. Such applications include various industrialapplications, such as torque transfer to and/or from an electric motor,a compressor, a pump, a gear drive, a transmission, and the like.Moreover, the present invention is not limited to internal combustionengine applications, but may be used with any form of power transmissiondevice, such as an electric motor of a vehicle equipped with an electricdrive motor.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are schematic illustrations of an overall view of thearrangements of an FEMG system in accordance with an embodiment inapplication Ser. No. 15/378,139.

FIGS. 2A-2C are cross-section views of an embodiment of aclutch-pulley-damper and assembled FEMG components in accordance with anembodiment in application Ser. No. 15/378,139.

FIGS. 3A-3C are views of the components of the FIGS. 2A-2Cclutch-pulley-damper unit.

FIGS. 4A-4B are oblique views of components of a polygonal coupling inaccordance with an embodiment of the present invention.

FIG. 5 is an oblique view of a component of a polygonal coupling inaccordance with another embodiment of the present invention.

FIGS. 6A-6B provide a cross-section view of an assembled embodiment ofthe polygonal coupling of the present invention.

FIG. 7 is an oblique view of another embodiment of a polygonal couplingin accordance with the present invention.

FIG. 8 is an oblique view of an embodiment of the present invention witha damping material integrated therein.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic illustration showing components of an embodimentof an FEMG system as in application Ser. No. 15/378,139. FIG. 1B is aschematic illustration of several of the FEMG system components in thechassis of a commercial vehicle. In this arrangement, the engineaccessories (including air compressor 1, air conditioning compressor 2and engine cooling fan 7 arranged to pull cooling air through enginecoolant radiator 20) are belt-driven from a pulley 5. The pulley 5 islocated co-axially with a damper 6 coupled directly to the crankshaft ofthe internal combustion engine 8. The accessories may be directly drivenby the drive belt or provided with their own on/off or variable-speedclutches (not illustrated) which permit partial or total disengagementof an individually clutch-equipped accessory from the belt drive.

In addition to driving the accessory drive belt, the pulley 5 is coupleda drive unit having reduction gears 4 to transfer torque between acrankshaft end of the drive unit and an opposite end which is coupled toa motor-generator 3 (the drive unit housing is not illustrated in thisfigure for clarity). A disengageable coupling in the form of a clutch 15is arranged between the crankshaft damper 6 and the pulley 5 (and hencethe drive unit and the motor-generator 3). Although schematicallyillustrated as axially-separate components for clarity in FIG. 1A, inthis embodiment the crankshaft 6, clutch 15 and pulley 5 axially overlapone another at least partially, thereby minimizing an axial depth of thecombined pulley-clutch-damper unit in front of the engine. Actuation ofthe pulley-clutch-damper clutch 15 between its engaged and disengagedstates is controlled by an electronic control unit (ECU) 13.

On the electrical side of the motor-generator 3, the motor-generator iselectrically connected to a power invertor 14 which converts alternatingcurrent (AC) generated by the motor-generator output to direct current(DC) useable in an energy storage and distribution system. The powerinvertor 14 likewise in the reverse direction converts direct currentfrom the energy storage and distribution system to alternating currentinput to power the motor-generator 3 as a torque-producing electricmotor. The inverter 14 is electrically connected to an energy storageunit 11 (hereafter, an “energy store”), which can both receive energyfor storage and output energy on an on-demand basis.

In this embodiment, the energy store 11 contains Lithium-based storagecells having a nominal charged voltage of approximately 3.7 V per cell(operating range of 2.1 V to 4.1 V), connected in series to provide anominal energy store voltage of 400 volts (operating voltage range ofapproximately 300 V to 400 volts) with a storage capacity of betweenapproximately 12 and 17 kilowatt-hours of electrical energy.Alternatively, the cells may be connected in series and parallel asneeded to suit the application. For example, 28 modules with fourseries-connected cells per module could be connected in series and inparallel to provide an energy store with the same 17 kilowatt hours ofstored energy as the first example above, but with a nominal operatingvoltage of 200 V volts and twice the current output of the firstexample.

In addition to the relatively high-capacity, low charge-discharge rateLithium-based storage cells, the energy store 11 in this embodimentincludes a number of relatively low-capacity, high charge-discharge rateof super capacitors to provide the energy store the ability over shortperiods to receive and/or discharge very large electrical currents thatcould not be handled by the Lithium-based storage cells (such cellsbeing typically limited to charge/discharge rates of less than 1 C toonly a few C).

FIGS. 2A-2C show cross-section views of an embodiment in applicationSer. No. 15/378,139 of the clutch-pulley-damper unit 19 and of anassembled configuration of FEMG system hardware with thisclutch-pulley-damper embodiment. In this embodiment the gearbox 16containing reduction gears 4 receives the motor-generator 3 at amotor-generator end of the gearbox. The motor-generator 3 is secured tothe housing of gearbox 16 with fasteners such as bolts (notillustrated). A rotor shaft 18 of the motor-generator 3 engages acorresponding central bore of the adjacent co-axially-located gear ofthe reduction gears 4 to permit transfer of torque between themotor-generator 3 and the reduction gears 4.

At the crankshaft end of the gearbox 16, the reduction gear 4 which isco-axially-aligned with the clutch-pulley-damper unit 19 is coupled forco-rotation to pulley side of the clutch-pulley-damper unit 19, in thisembodiment by bolts (not shown) passing through the co-axial reductiongear 4. The engine-side portion of the coupling (the portion having thecrankshaft damper 6) is configured to be coupled to the front end of theengine crankshaft by fasteners or other suitable connections that ensureco-rotation of the engine-side portion 6 with the crankshaft. Asdescribed further below, the gearbox 16 is separately mounted to astructure that maintains the clutch-pulley-damper unit 19 co-axiallyaligned with the front end of the engine crankshaft.

The cross-section view in FIG. 2B is a view from above the FEMG frontend hardware, and the oblique cross-section view in FIG. 2C is a view atthe crankshaft end of the gearbox 16. In this embodiment, the gearbox,motor-generator and clutch-pulley-damper unit assembly is arranged withthe motor-generator 3 being located on the left side of the enginecrankshaft and on the front side of the gearbox 16 (the side away fromthe front of the engine), where the motor-generator 3 may be locatedeither in a space below or directly behind the vehicle's engine coolantradiator 20. Alternatively, in order to accommodate different vehiclearrangements the gearbox 16 may be mounted with the motor-generator 3 tothe rear of the gearbox 16, preferably in a space laterally to the leftside of the engine crankshaft (for example, adjacent to the oil pan atthe bottom of the engine). The gearbox 16 further may be provided withdual-sided motor-generator mounting features, such that a common gearboxdesign may be used both in vehicle applications with a front-mountedmotor-generator and vehicle applications with the motor-generatormounted to the rear side of the gearbox.

FIGS. 3A-3C are views of the components of the clutch-pulley-damper unit19 of FIGS. 2A-2C. When assembled, the unit is unusually narrow in theaxial direction due to the substantial axial overlapping of the pulley5, engine-side portion 6 (hereafter, damper 6) and clutch 15. In thisembodiment the pulley 5 has two belt drive portions 21 configured todrive accessory drive belts (not illustrated), for example, one portionarranged to drive the engine cooling fan 7 surrounding the clutch 15,and another portion arranged to drive other engine accessories such asthe air compressor 1. The drive belt portions 21 in this exampleconcentrically surround the damper 6 and the clutch 15 (the belt driveportion 21 surrounding the damper 6 is omitted in FIGS. 2B and 2C forclarity).

Within the clutch-pulley-damper unit 19 the clutch 15 includes twoaxially-engaging dog clutch elements 25, 26. As shown in the FIGS. 2A-2Ccross-section views, the central core dog clutch element 25 is fixed forrotation with the damper 6, in this embodiment by bolts extendingthrough axial bolt holes 28 from the FEMG gearbox side of theclutch-pulley-damper unit 19. The pulley 5 is rotationally supported onthe central core element 25 by bearings 34.

An engine-side portion of the outer circumference of the central coredog clutch element 25 includes external splines 29 arranged to engagecorresponding internal splines 30 at an inner circumference of theaxially-movable dog clutch element 26. The external splines 29 andinternal splines 30 are in constant engagement, such that the movabledog clutch element 26 rotates with the damper 6 while being movableaxially along the damper rotation axis.

The movable dog clutch element 26 is also provided with axiallyforward-facing dogs 31 distributed circumferentially about the gearboxside of the element 26 (the side facing away from the engine). Thesedogs 31 are configured to engage spaces between corresponding dogs 32 onan engine-facing side of the pulley 5, as shown in FIG. 3C. The movabledog clutch element 26 is biased in the clutch-pulley-damper unit in anengaged position by a spring 33 located between the damper 6 and themovable dog clutch element 26, as shown in FIG. 2A. FIGS. 2B and 2C showthe clutch disengaged position, in which the spring 33 is compressed asthe movable dog clutch element 26 is axially displaced toward the damper6.

In this embodiment a clutch throw-out rod 27 is located concentricallywithin the central core dog clutch element 25. The engine-side end ofthe throw-out rod 27 is arranged to apply an axial clutch disengagementforce that overcomes the bias of spring 33 to axially displace the dogclutch element 26 toward the damper 6, thereby disengaging itsforward-facing dogs 31 from the corresponding dogs 32 at theengine-facing side of the pulley 5. In this embodiment, the gearbox endof the clutch throw-out rod 27 is provided with a bushing 303 and abearing 304 which enables the bushing to remain stationary while thethrow-out rod 27 rotates.

The clutch throw-out rod 27 is axially displaced to disengage and engagethe dog clutch 15 by a clutch actuator 22. In this embodiment the clutchactuator 22 is pneumatically-actuated, with compressed air enteringfitting 305 over clutch actuator diaphragm 41 and thereby urging thecenter portion of the diaphragm 41 into contact with the throw-out rodbushing 303 to axially displace the clutch throw-out rod 27 toward theengine to disengage the clutch 15. When compressed air pressure isremoved from the clutch actuator the diaphragm 41 retracts away from theengine, allowing the biasing spring 33 to axially displace the throw-outrod 27 and the dog clutch element 26 toward the pulley 5 to reengage theclutch dogs 31, 32 so that the pulley 5 co-rotates with the damper 6.

FIGS. 4A and 4B show an embodiment in accordance with the presentinvention of a polygonal coupling 90 between an input element of thetorque transfer segment (pulley-end gear 36) and an output element ofthe clutch-pulley-damper unit 19 (pulley 5). FIG. 4A illustrates thispolygonal coupling embodiment's male portion 91 carried on the gearboxpulley-end gear 36, and a female portion 92 formed in the opposingregion 96 of the pulley 5. The locations of the male and female portionsmay be reversed between the pulley 5 and the gearbox pulley-end gear 36.FIG. 4B is a reverse side view of the pulley 5 in FIG. 4A, showing theface of pulley region 96 that abuts the face of the gearbox pulley-endgear 36 containing the male portion 91.

The polygonal coupling male portion 91 includes a plurality ofaxially-aligned recesses 93, here arranged at the peaks of the lobes ofthe male polygon. The material between the recesses 93 and the outercircumference of the male portion 91 is undercut by grooves 94, suchthat elastically-deflectable arms 95 are formed on the periphery of thepolygonal coupling male portion 91. The recesses 93 are arrayed in bothdirections so that the male portion 91 has engineered flexibility inboth the forward and reverse rotation directions.

With this configuration, the present invention permits a small amount ofrelative rotation between the polygonal coupling male portion 91 andfemale portion 92, and hence between the pulley-end gear 36 and thepulley 5, while the broad surfaces of the sides of the polygon male andfemale portions ensure that the coupling can transfer a full torque loadbetween the pulley 5 and the pulley-end gear 36 as the crankshaftrotated. This relative rotation effectively de-couples the inertia ofthe torque transfer segment and the motor-generator from the crankshaftover the relatively small angular displacement of the crankshaft duringits vibrations (its micro-accelerations and decelerations), while stillmaintaining full torque transfer capability across the polygonalcoupling.

The recesses 93 in this embodiment are linear slots, which arerelatively easy to manufacture in a simple milling operation. However,the recesses are not limited to this shape. For example, the recessesmay be curved, and may have other features such as a broad circular endthat reduces local stresses and the potential for crack development overa large number flexing cycles of the arms 95. Similarly, the shape andwidth of the grooves 94 which separate the arms 95 from the face of thepulley-end gear 36 may vary in shape, height and depth as desired tosuit a particular application. Such variations of the recesses 93 andgrooves 94 are permissible as long as the configuration of the polygonalcoupling 90 is such that the arms 95 are capable of enduring a largenumber of flexing cycles over the design life of the polygonal coupling,and the recesses and grooves are sized to provide a degree offlexibility that permits the clutch-pulley-damper unit 19 to present adesired degree of torsional stiffness to the engine crankshaft.

The material of the polygonal coupling may be selected based on theamount of torque to be transferred across the coupling, the size of thepolygonal coupling components, the temperature in the operatingenvironment, etc. For example, in high torque applications and/or inapplications in which the male and female polygonal coupling portionsare small (thus increasing the local stresses at the mating surfaces ofthe male and female portions), a high-strength material such as steelmay be used to ensure sufficient longevity of the coupling.Alternatively, in lower torque loading and/or local stress applicationsin lower-temperature environments, other materials such as plastic orrubber coupling portions may be used. Further, mixtures of materials arepossible. For example, one of the male or female components may bedesigned as a sacrificial portion, so that in the event of overloadingof the polygonal coupling only the sacrificial side of the coupling isdamaged.

In a further embodiment of the present invention schematicallyillustrated in FIG. 5, the recesses 93 and arms 95 are provided on thefemale portion of the coupling, positioned such that the arms 95 may beelastically deformed outwards by the corners of the male polygon toaccommodate the desired small amount of relative rotation between thepulley 5 and the torque transfer segment gear 36 (which may have a solidmale portion of the coupling). As in the embodiment in FIG. 4, therecesses 93 must be sized and configured to endure a large number offlexing cycles over the design life of the polygonal coupling, whileproviding a degree of flexibility that permits the clutch-pulley-damperunit 19 to present a desired degree of torsional stiffness to the enginecrankshaft.

FIG. 6B presents a cross-section view of an embodiment of a polygonalcoupling as in FIG. 4A in an assembled state, taken along section lineA-A in FIG. 6A. In this view the male portion 91 of the gearboxpulley-end gear 36 is inserted into, and axially overlapped by, thefemale portion 92 in the region 96 of the pulley 5. In this state,engine crankshaft micro-accelerations/decelerations may be substantiallyabsorbed by the resilient arms 95 of the male portion 91 as the femaleportion 92 oscillates about the axis of rotation in response to thecrankshaft's motions.

FIG. 7 shows a portion of a coupling embodiment in which the torsionalstiffness of the coupling is increased relative to a coupling such asthat shown in FIG. 4A by not creating a slot between the arms 95 thatare radially outward of the recesses 93, but instead maintaining therespective pairs of arms 95 together at their apex 97 to form a morerotationally strong and stiff structure. The length and radial width ofthe arms may be increased or decreased relative to one another and/or inabsolute size, as necessary to obtained a desired amount of torsionalstrength and stiffness.

FIG. 8 shows another embodiment of a coupling similar to that shown inFIG. 4A, provided with a damping material 98 in the recesses 93 toprovide increased energy dissipation capacity and thereby increase thecoupling's ability to dampen movement caused by the engine's crankshaftvibrations.

The foregoing disclosure has been set forth merely to illustrate theinvention and is not intended to be limiting. Because such modificationsof the disclosed embodiments incorporating the spirit and substance ofthe invention may occur to persons skilled in the art, the inventionshould be construed to include everything within the scope of theappended claims and equivalents thereof.

LISTING OF REFERENCE LABELS

-   -   1 air compressor    -   2 air conditioning compressor    -   3 motor-generator    -   4 drive unit gears    -   pulley    -   6 damper    -   7 engine cooling fan    -   8 engine    -   9 vehicle batteries    -   10 DC/DC converter    -   11 energy store    -   12 battery management system    -   13 FEMG electronic control unit    -   14 AC/DC power inverter    -   15 clutch    -   16 gearbox    -   17 flange shaft    -   18 rotor shaft    -   19 clutch-pulley-damper unit    -   20 engine coolant radiator    -   21 belt drive portions    -   22 clutch actuator    -   23 clutch plates    -   24 clutch spring    -   25, 26 dog clutch elements    -   27 clutch throw-out rod    -   28 bolt holes    -   29 external splines    -   30 internal splines    -   31, 32 dogs    -   33 spring    -   34 bearings    -   90 polygonal coupling    -   91 polygonal coupling male portion    -   92 polygonal coupling female portion    -   93 recesses    -   94 grooves    -   95 arms    -   96 pulley outside face    -   97 apex    -   98 damping medium    -   303 bushing    -   304 bearing    -   305 fitting

What is claimed is:
 1. A polygonal coupling, comprising: an inputelement configured to transfer torque passing through the couplingsegment; an output element configured to rotate coaxially with the inputelement, wherein one of the input element and the output elementincludes a polygonal-shaped male portion of the polygonal coupling andthe other of the input element and the output element includes apolygonal-shaped female portion of the polygonal coupling, the femaleportion of the polygonal coupling is configured to axially overlap themale portion of the polygonal coupling along a rotation axis of theinput element, the female portion is configured to cooperate with themale portion to transfer torque across the polygonal coupling, at leastone of the male and female portions of the polygonal coupling includes aplurality of recesses configured such that elastically flexible arms areformed adjacent to lobes of the polygonal coupling, and the elasticallyflexible arms at each lobe are connected to one another adjacent to anapex of the respective lobe, and are configured to be displaced at leastone of radially inward and radially outward in a manner permittingrotation of the male and the female portions relative to one anotherabout the rotation axis.
 2. The polygonal coupling of claim 1, wherein:the input element is a rotating element of a component drivable bytorque transferred by the output element to the input element.
 3. Thepolygonal coupling of claim 2, wherein the component is an electricmotor, a compressor, a pump, a gear drive or a transmission.
 4. Thepolygonal coupling of claim 3, wherein: the rotating element is a shaftor a gear.
 5. The polygonal coupling of claim 2, wherein: the componentis a torque transfer segment of a hybrid electric front endmotor-generator system, and the output element is an output of aclutch-pulley-damper unit of the hybrid electric front endmotor-generator system.
 6. The polygonal coupling of claim 5, whereinthe input element is a gear of the torque transfer segment, and theoutput element is a pulley of the clutch-pulley-damper unit.
 7. Thepolygonal coupling of claim 1, wherein the male portion is at the inputelement, and the female portion is at the output element.
 8. Thepolygonal coupling of claim 1, wherein the female portion is at theinput element, and the male portion is at the output element.
 9. Thepolygonal coupling of claim 1, wherein the plurality of recesses areadjacent to the lobes of the male portion.
 10. The polygonal coupling ofclaim 1, wherein the plurality of recesses are adjacent to the lobes ofthe female portion.
 11. The polygonal coupling of claim 1, wherein theelastically flexible arms are configured such that the arms change anamount of arm displacement in response to changes in an amount of torquebeing transferred across the polygonal coupling.
 12. The polygonalcoupling of claim 11, wherein the elastically flexible arms areconfigured such that when the polygonal coupling is coupled to a powertransmission device, the elastically flexible arms change the amount ofarm displacement in response to changes in an amount of torque beingtransferred across the polygonal coupling caused by oscillatingrotational speed variations of the power transmission device.
 13. Thepolygonal coupling of claim 12, wherein the power transmission device isan internal combustion engine.
 14. The polygonal coupling of claim 13,wherein the output element is coupled to a crankshaft of the internalcombustion engine.
 15. A polygonal coupling, comprising: input means fortransfer of torque passing through the coupling segment; output meansfor transfer the torque to the input means, the output means beingarranged rotate coaxially with the input means, wherein one of the inputmeans and the output means includes a first polygonal-shaped torquetransfer means and the other of the input means and the output meansincludes a second polygonal-shaped torque transfer means, the secondtorque transfer means axially overlaps the first torque transfer meansalong a rotation axis of the input means and is arranged to cooperatewith the first torque transfer means to transfer torque across thepolygonal coupling, at least one of the first and second torque transfermeans includes a plurality of recesses configured such that elasticallyflexible arms are formed adjacent to lobes of the polygonal torquetransfer means, the elastically flexible arms at each lobe beingconnected to one another adjacent to an apex of the respective lobe, andthe first and second torque transfer means are rotatable relative to oneanother about the rotation axis.
 16. A polygonal coupling, comprising:an input element configured to transfer torque passing through thecoupling segment; an output element configured to rotate coaxially withthe input element, wherein one of the input element and the outputelement includes a polygonal-shaped male portion of the polygonalcoupling and the other of the input element and the output elementincludes a polygonal-shaped female portion of the polygonal coupling,the female portion of the polygonal coupling is configured to axiallyoverlap the male portion of the polygonal coupling along a rotation axisof the input element, the female portion is configured to cooperate withthe male portion to transfer torque across the polygonal coupling, atleast one of the male and female portions of the polygonal couplingincludes a plurality of recesses configured such that elasticallyflexible arms are formed adjacent to lobes of the polygonal coupling,the elastically flexible arms are configured to be displaced at leastone of radially inward and radially outward in a manner permittingrotation of the male and the female portions relative to one anotherabout the rotation axis, and a damping material is located in therecesses.
 17. The polygonal coupling of claim 16, wherein theelastically flexible arms at each lobe are connected to one anotheradjacent to an apex of the respective lobe.